Nowadays, the interest in the quality of the peripheral vision of the human eye (that is, what occurs outside the central zone where details are seen clearly) is greater than ever. This interest began in the 70's with the suggestion that peripheral vision could be an important factor that influences the progression of myopia (see, for example, the publication of F. Rempt, J. Hoogerheide, and W. P. H. Hoogenboom, “Peripheral Retinoscopy and Skiagram”, Ophthalmologica 162, 1-10 (1971), or the publication of J. Hoogerheide, F. Rempt, and W. P. H. Hoogenboom, “Acquired Myopia in Young Pilots”, Ophthalmologica 163, 209-215 (1971)).
To investigate said suggestion, several laboratories conducted tests with animals, as can observed in the following publications:                F. Schaeffel, A. Glasser and H. C. Howland, “Accommodation, refractive error and eye growth in chickens”, Vision Res. 28, 639-657 (1988).        S. Diether and F. Schaeffel, “Local changes in Eye Growth induced by Imposed Local Refractive Error despite Active Accommodation”, Vision Res. 37, 659-668 (1997).        E. L. Smith, C. Kee, R. Ramamirham, Y. Qiao-Grider and L. Hung, “Peripheral Vision Can Influence Eye Growth and Refractive Development in Infant Monkeys”, Invest. Ophthalmol. Vis. Sci. 46, 3965-3972 (2005).        E. L. Smith, R. Ramamirtham, Y. Qiao-Grider, L. Hung, J. Huang, C. Kee, D. Coats and E. Paysse, “Effects of Foveal Ablation on Emmetropization  and Form-Deprivation Myopia”, Investigative Opthalmology & Visual Science 48, 3914-3922 (2007). D. O. Mutti, R. I. Sholtz, N. E. Friedman and K. Zadnik, “Peripheral Refraction and Ocular Shape in Children”, Investigative Opthalmology & Visual Science 41, 1022-1030 (2000).        
The importance of peripheral vision in the progression of myopia has been reproduced in tests involving primates and other animals. With regard to experiments carried out on the human eye, several research groups have found correlations that may indicate that an eye that has relatively more hypermetropia in the peripheral retina than in the fovea has a greater likelihood of developing myopia, in accordance with the following publications:                A. Seidemann, F. Schaeffel, A. Guirao, N. Lopez-Gil and P. Artal, “Peripheral refractive errors in myopic, emmetropic, and hyperopic young subjects”, J. Opt. Soc. Am. A 19, 2363-2373 (2002).        J. Wallman and J. Winawer, “Homeostasis of Eye Growth and the Question of Myopia”, Neuron 43, 447-468 (2004).        D. A. Atchison, N. Pritchard, K. L. Schmid, D. H. Scott, C. E. Jones and J. M. Pope, “Shape of the Retinal Surface in Emmetropia and Myopia”, Investigative Opthalmology & Visual Science 46, 2698-2707 (2005).        D. O. Mutti, J. R. Hayes, G. L. Mitchell, L. A. Jones, M. L. Moeschberger, S. A. Gotter, R. N. Kleinstein, R. E. Manny, J. D. Twelker and K. Zadnik, “Refrective Error, Axial Length, and Relative Peripheral Refractive Error before and after the Onset of Myopia”, Investigative Opthalmology & Visual Science 48, 2510-2519 (2007).        L. Lundström, A. Mira-Agudelo and P. Artal, “Peripheral optical errors and their change with accommodation differ between emmetropic and myopic eyes”, Journal of Vision 9(6):17, 1-11 (2009).        X. Chen, P. Sankaridurg, L. Donovan, Z. Lin, L. Li, A. Martinez, B. Holden and J. Ge, “Characteristics of peripheral refractive errors of myopic and non-myopic Chinese eyes”, Vision Res. 50, 31-35 (2010).        W. N. Charman, H. Radhakrishnan, “Peripheral refraction and the development of refractive error: a review”, Ophtal. Physiol. Opt. 30, 321-338 (2010).        
Due to hypermetropia in the peripheral retina, the image is focused behind the retina. To obtain a focused image, the peripheral retina of the eye grows in order to compensate it, while at the same time it pushes the central retina back producing myopia. The first study with children who wear classes developed specifically for eliminating hypermetropia on the peripheral retina with the aim of preventing the progression of myopia corresponds to the publication by P. R. Sankaridurg, L. Donovan, S. Varnas, X. Chen, Z. Lin, S. Fisher, A. Ho, J. Ge, E. Smith and B. A. Holden, “Progression of Myopia With Spectacle Lenses Designed to Reduce Relative Peripheral Hyperopia: 12 Months Results”, ARVO 2010 abstract, program # 2206.
Spanish patent application 200900692 referred to a “Device for Asymmetrical Refractive Optical Correction in the Peripheral Retina for Controlling the Progression of Myopia”, develops another version of these devices for prophylaxis and prevention of myopia in children and/or adolescents. In effect, the optical device is a modifier of the peripheral retina of the eye for prophylaxis of the progression of myopia, consisting of a lens that in its inferior nasal quadrant progressively modifies the strength of the lens. The rest of the quadrants of the device present a graduated glass or flat glass configuration, depending on whether the user has a visual defect that requires optical correction or lacks said defect, respectively. The lens can either be an optical lens, a contact lens, or electro-optic systems.
Currently, the most used technique for measuring ocular aberrations is based on the so called Hartmann-Shack wavefront sensor. Said method is employed in many research laboratories throughout the world, and is also the most frequently used in commercially available systems. It consists in a micro-lens matrix that is optically conjugated with the pupil of the eye, and a camera placed on the focal plane of the micro-lenses. If a flat wavefront reaches the sensor, the camera registers a perfectly regular point distribution, whereas if the wavefront is deformed (that is, it has aberrations) the point distribution will be irregular. Mathematically, the displacement of each point is directly proportional to the derivative of the wavefront from each micro-lens. Wave aberrations are calculated from the images of the points.
To correctly investigate the impact of peripheral vision it is important to have instruments available that are capable of measuring it rapidly and with the necessary precision. Previously, instruments developed for measuring the refraction and/or aberrations of the central vision (on the fovea) were used. The only difference is that they require the subject to look at different angles in sequence while the fixed instrument takes the measurements. The measurements require a good deal of time (several minutes) and in order to shorten the time, the number of angles is reduced, which results in poor angular resolution. Furthermore, there are questions about whether rotating the eye changes the aberrations due to the tension of the eye muscles on the optics of the eye.
There is a demand for instruments that explore all eye angles so as to improve the measurements. The main difference between a static system and a scanning system is that in the first the subject needs to change his line of sight, whereas in the second, it is the instrument that changes it position to measure other angles.
There are two known instruments that perform a scan for measuring peripheral optical quality of the eye. The “peripheral photorefractor”, in the document of J. Tabernero and F. Schaeffel, “Fast scanning photoretinoscope for measuring peripheral refraction as a function of accommodation”, J. Opt. Soc. Am. A. 26, 2206-2210 (2009), is a system that only measures eye refraction on one meridian of the pupil. The instrument moves in a linear translation while rotating a beam splitter. It has a 90° scanning range. The advantages of the system are that it has a large scan field and that the alignment of the subject is less critical; however, it has several important drawbacks. The operating base of the method is empirical, and the calibration of the reflection of the light off the back of the eye is essential for obtaining correct results. Also, only the refraction from one meridian can be measured. That is, it provides very partial measurements of the peripheral optics of the eye. Moreover, due to its design, a mirror moves in front of the subject, a situation that could give rise to errors when used on subjects who lack experience, as they will tend to follow it during the measurement.
The other scanner, disclosed in the document of X. Wei and L. Thibos, “Design and validation of a scanning Shack Hartmann aberrometer for measurements of the eye over a wide field of view”, Optics express 18, 1134-1143 (2010), measures aberrations of the eyes with the Hartmann-Shack (HS) technique. As mentioned above, this technique measures the wavefront that leaves the eye (see the documents of J. Liang, B. Grimm, S. Goelz and J. F. Bille, “Objective measurement of wave aberrations of the human eye with the use of a Hartmann-Shack wave-front sensor”, J. Opt. Soc. Am. A 7, 1949-1957 (1994); P. M. Prieto, F. Vargas-Martin, S. Goelz, P. Artal, “Analysis of the performance of the Hartmann-Shack sensor in the human eye”, J. Opt. Soc. Am. A, 17, 1388-1398 (2000)). The advantages of the instrument are that the only moveable objects are two mirrors and that all of the aberrations are measured, as well as the refraction. The camp being measured is not only the nasal and temporal retina, but also the inferior and superior retina. The drawbacks are that the measurements have a very low density, as only a 30° field can be measured, which is too little to form a good idea of the peripheral vision. This system, which has already been published, covers a small field and is slow (it requires 8 seconds to measure 37 angles).
Consequently, there is a need to have an instrument at hand to measure optical properties of the eye, refraction and aberrations, which is quick, robust, precise, and simple, and which makes it possible to take measurements on a broad visual field.